Many concrete surfaces whether in parking lots, over bridges, on tunnel walls, building walls or any other concrete surface are frequently accompanied by heavy steel reinforcement. Once cracks in the concrete develop, road salts corrode the steel. This corrosion accelerates the destructive cycle of moisture, salt, freeze-thaw, corrosion, vibration and traffic. Conventional methods of repairing these concrete surfaces involves first the removal of the deteriorated concrete surface around and below the reinforcing steel bars. This removal allows placement of new concrete surface over the reinforcing steel.
Ordinarily concrete removal has been accomplished by jackhammers, but the use of jackhammers is time-consuming, and costly and makes it difficult to achieve complete removal of deteriorated concrete. In addition, the use of a jackhammer causes microcracking of the remaining concrete in surrounding areas. In order to improve the speed and efficiency of concrete removal from bridge decks, highways, substructures and parking garages and, at the same time, avoiding the problems caused by microcracking, contractors began using high pressure water jets to remove the concrete. The use of high pressure water jets, termed hydrodemolition, involves moving an oscillating or rotating nozzle back and forth across a bed for a number of passes and then indexing or advancing a vehicle on which the bed and nozzle are supported to a next position where the process is repeated until a desired depth of concrete deck surface has been removed. The removal leaves clean reinforcing rod which has been descaled but otherwise undamaged and a rough textured concrete surface under the reinforcing rod which is ideal for bonding of new overlay. All deteriorated concrete is removed and entrained chlorides washed away. There is a greatly reduced noise and no vibration or dust.
The conventional equipment used in hydrodemolition has one nozzle which runs over a guide bed and traverses a swath to be treated. After each pass the machine is indexed until a region has been impacted by one traversal. The vehicle is then reversed and the process repeated with the machine moving in indexes in reverse. Again once the swath has been covered the vehicle is moved forward in an indexed manner and traversals of the nozzle are repeated until the swath has been covered three times. Ordinarily three such passes are required to complete the hydrodemolition. Since the cost of a job is directly proportional to the time taken to accomplish it, there is a need for a faster more efficient method of applying hydrodemolition than that currently used. Some conventional equipment will complete a number of passes in a given position before being indexed forward where a like number of passes is then completed.
Accordingly, it is an object of the invention to provide an improved method and apparatus for applying hydrodemolition. It is a further object to provide a faster method of treating a surface with hydrodemolition than is currently in use.